Predicate Encryption System Concealing Attribute and Predicate Data
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Solution Overview
Problem
There is no implementation of predicate encryption that can conceal both attribute information in a ciphertext and predicate information in a decryption key in a public key setting, where the encryption-side key is made public.
Innovation Solution
A cryptographic system is developed with an encryption device generating a ciphertext with attribute information as a coefficient of a basis vector, a conversion device converting the ciphertext using conversion information to another basis, and a decryption device decrypting the converted ciphertext with a token containing predicate information as a coefficient of a corresponding basis vector, allowing for the concealment of both attribute and predicate information in a public key setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If predicate encryption is implemented in a public key setting where the encryption-side key is made public, then the encryption device can use a public key for encryption, but the predicate information in the decryption key may be leaked during search operations
Solution Approach 1:
The system segments the decryption key into multiple components: a public token component that can be freely distributed for search operations, and a private key component that remains secret. The predicate information is embedded only in the public token component, allowing multiple users to perform searches without exposing the underlying predicate logic. This segmentation resolves the contradiction by enabling public key operations while protecting predicate information through structural separation.
Solution Approach 2:
The patent introduces a basis conversion mechanism as an intermediary between the public token and the private key. The conversion information (basis transformation data) acts as a mediator that allows the decryption device to translate public token operations into private key operations without directly exposing the predicate information. This intermediary layer enables public key functionality while maintaining predicate privacy through indirect operation translation.
2Adaptability or versatility
If the encryption-side key is made public to enable widespread encryption, then encryption accessibility is improved, but the security of predicate information in decryption keys is compromised
Solution Approach 1:
The decryption key is segmented into a public token portion and a private key portion. The public token can be freely distributed to multiple encryption devices, enabling widespread encryption accessibility. The private key portion containing the sensitive predicate information remains secure and is never exposed. This segmentation allows the system to achieve both high adaptability and reliability simultaneously.
Solution Approach 2:
The system transitions from a single-dimensional key structure to a multi-dimensional key structure with public and private components operating in different dimensions. The public token operates in the public dimension where accessibility is prioritized, while the private key operates in the secure dimension where reliability is maintained. This dimensional separation resolves the contradiction between accessibility and security.
3Ease of operation
If predicate information is embedded in the decryption key for secure search, then search functionality is enabled, but the predicate information may be exposed when the encryption key is public
Solution Approach 1:
The search functionality is enabled through a public token that contains encoded predicate information in an obscured form. The token structure segments the predicate representation into a public component that can be used for search operations and a private component that remains protected. This allows search functionality to operate on the public component without exposing the actual predicate logic stored in the private component.
Solution Approach 2:
The predicate information undergoes parameter transformation through basis conversion. The original predicate representation is transformed into a different basis where the same search functionality is achieved but the information is represented in a protected form. This parameter change allows the system to maintain search capability while preventing direct exposure of the predicate information.
Data Source
AI summary
It is an object to provide predicate encryption that can conceal both attribute information being set in a ciphertext and predicate information being set in a decryption key even in a public key setting. An encryption device 200 generates a ciphertext ctx in which attribute information x is set as a basis vector of a basis D. A conversion device 300 converts with conversion information W the basis D of the ciphertext ctx generated by the encryption device 200 to a basis B so as to generate a ciphertext CTx. A decryption device 400 decrypts the ciphertext CTx generated by the conversion device 300 with a token tkv in which predicate information v is set as a coefficient of a basis vector of a basis B* corresponding to the basis B.